The present invention relates to a process for forming musical tones in an electronic musical instrument.
Digital waveshape syntheses and digital waveshape processings for forming musical tones are disclosed, for example, in a U.S. Pat. No: 3,809,786 entitled COMPUTOR ORGAN by Ralph Deutch et al., and a U.S. Pat. No: 3,878,749 entitled WALSH FUNCTION TONE GENERATOR AND SYSTEM by Robert P. Woron.
In all these heretofore known waveshape syntheses and processings, all the data-processings are performed on a time domain, where a waveshape is expressed as a function of time. Data-processings on a time domain are sometimes confronted with difficulties in hardware designs. For example, when a digital filter is required for a data-processing in a time domain, it often becomes difficult to build a digital filter of the requirement. As will be easily understood, a filter used in a data-processing to form a desired tone waveshape must have a high degree characteristic, for example, a sharp cutoff characteristic. A digital filter is composed of delay elements, attenuator elements, and adder elements; and numbers of these elements are required to compose a digital filter of a high degree characteristic; and therefore, the filter will become bulky and expensive.